1. Field of the Invention
The present invention relates to remote controls for electronic devices and, more particularly, to remote control transmissions.
2. Description of the Related Art
In modern consumer electronic devices such as television receivers, set-top boxes (e.g. cable boxes, satellite receivers, stereos, etc.) and the like (collectively, consumer electronic devices) many functions and/or features may be accessed and/or controlled via a remote control device. The remote control device may be user-actuated, as in the case of a hand-held remote control, or it may be device-actuated, in the case of a “relay” type remote control. In both cases, the remote control generates and transmits (wirelessly) a remote control signal that is received by the receiving electronic device. The control signal is encoded/coded in a manner appropriate for the receiving device. The receiving device receives the encoded/coded control signal and performs the requested command.
The remote control may use a variety of wireless transmission mediums in order to send or transmit the generated control signal from the remote control to the receiving electronic device. One type of remote control uses bursts of infrared (IR) light or radiation as the medium/vehicle for transmission of the encoded signals, which are received by a suitable receiving device associated with the consumer electronic device. The consumer electronic device may include a microprocessor for performing many receiver functions in addition to decoding received IR coded command signals and generating appropriate control signals in response thereto. An IR encoded command signal generally consists of a binary data stream of given word length in which the presence of a burst of infrared energy represents a binary 1 and the absence of infrared energy represents a binary 0.
IR transmissions from a remote control are typically made up of a series of pulses (high voltage/binary 1) and spaces (low voltage/binary 0) of varying lengths. Different combinations of the pulses and spaces are used to create unique IR codes. Each unique IR code represents a different key on the remote control. Consumer electronic devices may or may not use the same codes for the same or similar features. Thus, a remote control for one electronic device may not necessarily work with another electronic device.
A typical remote control includes transmitter circuitry that may be part of an integrated circuit (IC) and, more particularly, an application specific integrated circuit (ASIC). For typical transmissions utilizing the IR circuitry, the length of the pulse and the length of the space are individually specified in separate registers. The registers are loaded with a pulse/space combination when a key on the remote control is actuated. When an IR sequence is being transmitted, an interrupt is generated at the end of each pulse-space combination. At the time of the interrupt, the next pulse-space sequence or combination is loaded from user registers to transmission registers. At this time, it is safe for the remote to reload the user pulse and space registers so they are set up for the next pulse-space combination, which is the loaded at the next interrupt.
A problem with typical remote control circuitry that operates in the above manner, is that the IR transmitter only has a range of about ten microseconds (10 μsec) as a minimum to ten milliseconds (10 msec) as a maximum, in ten microsecond (10 μsec) increments, for each the pulse and space. However, some IR formats require space and pulse times greater than ten milliseconds. Since the minimum space or pulse time is only 10 microseconds instead of zero (0), the spaces or pulses cannot be concatenated to achieve spaces or pulses, respectively, greater than ten milliseconds.
It has been determine that a pulse greater than ten milliseconds may be provided by two pulses with a single ten microsecond space therebetween without creating a problem for the receiving device. Particularly, as an example, a ten microsecond drop in a ten millisecond pulse is less than one cycle (assuming a carrier of 56 KHz, the period is 17 μsec). However, it has determined that providing just a ten microsecond pulse between two spaces causes a discrimination problem for the remote control transmission receiver.
It is thus desirable to have a remote control that is operative to provide remote control transmissions of pulses and/or spaces that exceed the maximum pulse and/or space duration.
It is thus also desirable to have a method of transmitting a remote control signal when a pulse and/or space exceeds the maximum pulse and/or space duration.